Efficiency enhancement techniques for mm-Wave CMOS PAs: A tutorial

© 2016 IEEE. With advances of CMOS technologies, the high-speed characteristic of transistors gives additional design margin for millimeter-wave (mm-Wave) PAs. The design of prior-art mm-Wave PAs is now focusing on the optimizations of back-off efficiency while maintaining linearity. This facilitates the transmission of broadband high-order digital modulated signals with decent system efficiency. This paper reviews three recently reported efficiency enhancement techniques at mm-Wave, including Doherty PA, outphasing PA and digital PA. The design challenges encountered at mm-Wave will be discussed and the proposed circuit techniques will be detailed. The benefits of these techniques are confirmed by the measured results of state-of-the-art PA design examples. Outlook and future trends of CMOS mm-Wave PAs will also be discussed.status: publishe